reading from standard input in batch mode

[Eric Abrahamsen <eric@ericabrahamsen.net>]

I'm trying to figure out how batch mode works, and I want to do
something very simple: call a subordinate emacs process, passing it a
string, and have it write the string to a file. It's not working but I
don't know how to debug this.

In boomerang.el:

(defun boomerang ()
  (let ((msg (read)))
    (append-to-file msg
		    nil
		    "/home/eric/tmp/results.txt")))

In my main emacs:

(shell-command
"emacs -Q --batch -l boomerang.el -f boomerang \"hi there\"")

The subordinate emacs starts and finishes (returning 255, which just
came up on a thread in emacs.devel, I think), but no file is written. As
far as I know, `read' should be reading from standard-input in this
case. What am I doing wrong?

Thanks,
Eric